1994 F150 - I6 300 - E4OD - 173k Miles, Original Motor and Transmission

Transmission started to slip out of gear entirely the other day and quite suddenly. Only when I gave it extra throttle (1500-2000 RPM) would it shift into gear. It would have trouble engaging, and would drop out of gear at low RPM. Fluid had good quantity (high if anything). This was true for Reverse and forward gears. Felt like a very low fluid level, but since it started suddenly, I started thinking electrical...

I had driven through a lot of rain and thought maybe it was a puddle that shorted the electrical, so I started there:

No Codes, KOEO and KOER, no check engine light.

Replaced original MLPS (I had purchased one a year ago for what was an intermittent shift into neutral, but never ended up installing it since the problem cleared on its own).

Inspected and Cleaned/Dried solenoid connector, tested the TPS with multimeter, tested good even while running and slipping.

So then, I decided to get a look at the fluid: Drained about 1 Quart out of the torque converter (so i didn't have to undo all those dang bolts). Fluid looked and smelled fine. I had changed it about 2 years (25k miles) ago. Dipstick still looked full when running, but the shifting problem got a little worse. I really couldn't get it into gear. Now I'm thinking the I've got a low fluid issue. I added back a fresh quart of Mercon V and another 3/4 quart.

Dipstick is showing me to be stupidly over-full, but the transmission shifts. It's still slipping a bit between first and second, and it stumbles a bit when I throw it in Reverse, but for the most part is running again. Downshifting is normal.

I'm pretty certain I'm checking the fluid properly, engine/tranny up to temp, shifter neutral, level ground. But I'm nervous to add any more fluid to see if it will shift any better. Either I have the wrong dipstick or I'm thinking there's a major flow restriction that I'm not getting. Is there any other situation that would cause this?

Any help would be awesome.

 

Since that trans is computer controlled and the problem seems to be sensitive to throttle position I'd suggest changing the TPS, if there is a dead spot in the travel the computer will do strange things.

Is the speedo or ODO doing anything abnormal which is to say anything except working perfectly?

 

Thanks for the reply. Speed and ODO are fine. No weird stuff there. I had tested the TPS with voltmeter, and it got the 5 ref volts needed, swung from .98v idle up to the proper voltage (12 I think) when WOT.

 

Smoothly with no dead spots ... Analog meter works best for this!

-Enjoy
fh : )_~

 

I need to check that then. I'll actually just replace the thing at a cost of $15 and take it back if it doesn't work

 

You didn't say if the engine is running or not. If it is, you're checking the level correctly. If it isn't, the readings you are getting are totally meaningless. And I always check it with the shifter in park, though that won't make a difference in the reading.

 

Yes, I'm checking it while running. I put the transmission through all the gears first, as well.

OD button and light is functional, never seems to enter limp mode

 

Transmission dipsticks can be very hard to read, especially if you recently put fluid in.

Usually what happens, is that one side ends up collecting a bunch of fluid and makes it look like the transmission is full. Often if you look at the back side of the stick, you'll see that the transmission is actually not full. Compare both sides of the stick, and add fluid until both sides are in the cross-hatches.

 

Unfortunately, both sides of the stick are about 1/4 inch or more above the top of the hashed area.

 

Other symptoms I've noticed as a pattern:

When cold (after the computer finishes the warm-up), the engine stumbles and occasionally stalls when trying to put the transmission in either Drive or Reverse. Once engaged, the engine fluctuates about 200-300 RPM and seems to hunt for a stable speed. During this time, the transmission will slip when accelerated.

After cruising in 3rd or OD and coming to a full stop, the transmission downshifts twice (presumably 2nd then 1st), with an associated RPM stumble each shift, like a heavy load was being added. Early in the drive it stalled the engine. Also, when I rechecked the fluid yesterday there were a few bubbles in the fluid. I cannot discern a burned smell yet, but the fluid is still pink.

The problems appear lessened as the vehicle warms up. By the time I drove 20 miles, it almost appeared normal. Unfortunately, I'm starting to feel like this is mechanical.

 

You should not be able to feel downshifts into 2nd or 1st with the shifter in "Drive", since the over-running clutch in the OD section causes the transmission to free-wheel.

I would get a multimeter out and check continuity between the MLPS pins and the main EEC computer connector.

 

What would the implication of that be? That the gears aren't disengaging while coasting?

I don't notice any load on the transmission while coasting. All appears normal. But once I get to a stop, I get the bumps.

 

The transmission should be in first gear before coming to a stop. It should not shift after stopping.

 

Could low line pressure cause that kind of delayed reaction?

BTW, thanks for the assistance, everyone. I really appreciate the help trying to diagnose this one.

 

Even when stopped, you shouldn't be able to feel the transmission shift. It sounds like you're losing line pressure at idle and the transmission is slipping in and out of gear.

I'd drop the pan and check the filter. They have been known to fall out sometimes.